Transformer



L. W. MARKS June 17, 1952 TRANSFORMER Filed Sept. 17, 1949 ER 25 mm I hvent ors K r a M W m u o L H is Attorney Patented June 17, 1952TRANSFORMER Louis W. Marks, Pittsfield, Mass, assignor to GeneralElectric Company, av corporation of New York Application September 17,1949, Serial No. 116,380

4 Claims. (01. 175-358) My invention relates to transformers and,although not limited thereto, it has particular application to highvoltage instrument transformers.

Heretofore, high voltage current transformers have been made with highvoltage winding and core structures which are wound With their axesperpendicular to, the axis of the cylindrical enclosing casing. Thecasing which is usually used is of porcelain or otherinsulatingmaterial. Due to the above mentioned positionin of the coiland core, certain portions of these components are much nearer to theinterior surfaces of the enclosing casing than are other portions. Thiscircumstance gives rise to an uneven peripheral voltage distributionaround the exterior of the casing, and the resulting existence of localareas of high voltage stress concentrations increases the incidence ofcorona effects. These corona effects and the accompanying ionization ofthe surrounding air are very undesirable since they increase theprobability of an actual fault condition and subsequent breakdown ofthe. entire insulation system.

It is, therefore, an object of my invention to eliminate the unevenperipheral voltage distribution around the exterior of a high voltagetransformer.

My invention consists essentially of a high voltage transformerstructure including a cylindrical equi-potential conducting surfacewhich may be embedded within a suitable insulating material and insertedbetween the coil and core of the transformer and the interior of thetransformerenclosing casing.

My invention will be more fully set forth in the following descriptionreferring to the accompanying drawing, and the features of novelty whichcharacterize my invention will be pointed Out in the claims annexed toand forming a part of this specification.

In the drawing Fig. 1 is a side elevation, in partial section, of a highvoltage instrument transformer embodying my invention; Fig, 2 is abottom view in partial section of the transformer illustrated in Fig. 1;and Fig. 3 is a graph showing the uneven peripheral potentialdistribution which exists in the absence of the structure of myinvention and the comparatively even voltage distribution which occurswith the structure of my invention,

Referring to the drawing, in Fig. 1, I have illustrated a high voltageinstrument transformer designated as a whole as I, which includes aprimary winding 2 and a secondary Winding 3 which is distributed arounda suitable core 4. Windings 2 and 3 are each annular-shaped, with theaxes of the respective windings being aligned mutually perpendicularlytov each other and to the axis of the casing in which the windings arepositioned. The two annular-shaped windings are structurally interlinkedwith each other, due to the fact that each winding passes through, thehollow portion of the other winding. Extending from the primary windingand connected thereto, I provide suitable lead members 5 whose ends areconnected to the connectors 6 which are in turn connected in the highvoltage lines whose current or voltage is to be measured or controlled.The Winding core and terminal leads are suitably housed in a casing 1which is comprised of a tubular porcelain bushing 8 and a steel casingend member 9. Windings 2 and 3 are surrounded by insulation ill of anysuitable type such as crepe paper which may be applied in any suitablemanner such as by; winding in tape form to the desired thickness. Thesame type of insulation may also. be wound around the leads 5. Thecasing 7 may be filled with a suitable dielectric, fluid, such as oil,to the level II and a conservator I2 is provided at the top of thebushing 8 tov allow for thermal expansion and contraction of the fluid.

Surrounding the coils 2 and 3 and thecore 4 is an equi-potentialcylinder M, which may be. of any suitable insulating material such as aresin bonded paper laminate, within which a cylindrical conductingsurface I5 isembedded which may consist of a graphite phenolic resinvarnish or other suitable conducting material. Surface [5 need not be aperfect conductor, but may have considerable resistance and stillperform the function described below. The cylinder M with its embeddedconductor I5, therefore forms an equi-potential surface which surroundsthe coils and core within casing 1 and the potential distribution aroundthe exterior of this equi-potential cylinder and therefore around theexterior of the casing 1 is practically constant.

In Fig. 2 is shown a bottom view of my transformer with the casing andequi-potential cylinder shown in section. This view shows how certainportions of the transformer coils are spaced much more closely to thetransformer casing than are other portions of the transformer coils.Around the periphery of my transformer, as shown in Fig. 2, potentialmeasurement positions have been marked with letters, A through H. at 45intervals. When potential measurements are taken from these respectivepositions to ground,

the circumferential potential distribution curve at section 2-2 on Fig.1 such as curve l6 shown in Fig. 3 may be plotted. In contrast, curve I!in this same figure shows how uneven the voltage distribution is in acorrespondin transformer which is not equipped with the equi-potentialcylinder of my invention.

It will be obvious of course that conducting surface l5 could bepositioned around the exterior of equi-potential cylinder l4 instead ofembedded therein.

My invention, therefore, virtually eliminates unequal peripheral voltagedistribution around the exterior of high voltage instrument transformersin the vicinity of the transformer coils, thus eliminating dangerouscorona discharge and fault producing tendencies without appreciablyincreasing the size, weight or cost of the transformer.

Although I have shown and described a particular embodiment of myinvention, I do not desire to be limited to the particular embodimentdescribed and I intend in the appended claims to cover all modificationswhich do not depart from the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

1. In a high-voltage instrument transformer, a first annular-shapedelectrical winding and a second annular-shaped electrical winding, oneof said windings being positioned on an annularshaped magnetic corestructure, said first; and second windings being structurallyinterlinked with each other, the axis of said first winding beingperpendicular to the axis of said second winding, a hollow insulatingcasing surrounding and enclosing said first and second windings, thelongitudinal axis of said insulating casing being perpendicular to therespective axes of said first and second windings, an insulating liquidwithin said casing, said windings being immersed in said liquid, aconductively isolated hollow cylindrical conductor member containedwithin said casing, said hollow cylindrical conductor member beingcoaxial with said casing, said hollow cylindrical conductor membersurrounding said windings and core structure.

2. In a high-voltage instrument transformer, a first annular-shapedelectrical winding and a second annular-shaped electrical winding, oneof i said windings being positioned on an annularshaped magnetic corestructure, said first and second windings being structurally interlinkedwith each other, the axis or" said first winding be ing perpendicular tothe axis of said second winding, a hollow insulating casing surroundingand enclosing said first and second windings, the longitudinal axis ofsaid insulating casing being perpendicular to the respective axes ofsaid first and second windings, an insulating liquid within said casing,said windings being immersed in said liquid, a conductively isolatedhollow cylindrical conductor member contained within said casing, saidhollow cylindrical conductor member being coaxial with said casing, saidhollow cylindrical conductor member surrounding said windings and corestructure, said hollow cylindrical conductor member being completelyembedded in a solid insulating material.

3. In an instrument transformer comprising a hollow insulating enclosingcasing, a first annular-shaped electrical winding positioned within saidcasing, a second annular-shaped electrical winding positioned withinsaid casing and structurally interlinked with said first winding, one ofsaid windings being wound about an annular-shaped magnetic core, theaxes of said first and second windings and of said enclosing casing allbeing mutually perpendicular to each other, an insulating liquid withinsaid casing, said windings being immersed in said liquid, a conductivelyisolated open cylindrical equipotential conductor member positionedwithin said casing substantially coaxially with said casing, saidcylindrical conductor member surrounding said first and second windingsand said magnetic core.

4, In an instrument transformer comprising a hollow insulating enclosingcasing, a first annular-shaped electrical winding positioned within saidcasing, a second annular-shaped electrical winding positioned withinsaid casing and structurally interlinked with said first winding, one ofsaid windings being wound about an annular-shaped magnetic core, theaxes of said first and second windings and of said enclosing casing allbeing mutually perpendicular to each other, an insulating liquid withinsaid casing, said windings being immersed in said liquid, a conductivelyisolated hollow cylindrical equipotential conductor member positionedwithin said casing substantially coaxially with said casing, saidcylindrical conductor member surrounding said first and second windingsand said magnetic core, said cylindrical conductor member beingcompletely embedded in a solid insulating materia LOUIS W. MARKS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,394,910 Kierstead Oct. 25, 19211,657,249 Eby I Jan. 24, 1928 1,701,334 Palueff Feb. 5, 1929 1,873,049Schrader Aug. 23, 1932 1,889,552 Keinath et a1 Nov. 29, 1932 2,280,625Camilli Apr. 21, 1942

